Hillshade

calculates a hillshade for a DEM (matrix)

Function to calculate hillshade for a digital elevation model. Derives slope and aspect in radias to calculate shading value between 0 and 255 using a given lighting angle and altitude.

Altitude (angle above ground) and angle (direction/aspect) of lightsource can be given via args.

Derived using ESRIs hillshade algorithm, but uses simple GRADIENT function instead of Horns algorithm for slope calculation - factor 30 more efficient & no need for IP TB. (Thanks to Andrew Stevens)

Pls leave you feedback/rate.